Mortal Wounds is only triggered by Mortal Strike (Arms Warrior), Wild Strike (Fury Warrior) or Rising Sun Kick (Windwalker Monk). The other two spells that fall into this category do not trigger the category debuff but apply their own debuffs instead:

The wowhead guide is not that good as it gives the trigger spells' spell ids, which are not always the debuff ids. Some examples:
Wound Poison is listed there as 8679, which is the spell and buff id. The corresponding debuff id is 8680.
Mind-numbling Poison listed as 5761, which is the spell and buff id. Debuff id is 5760.
Master Poisoner's debuff id is 93068.

There are maybe others too, haven't checked them all yet. The links in my post have the correct debuff ids. As for the pet debuffs, you could trust the info in the guide as pet debuff ids are always the same as the spell id (at least I haven't found an exception to this yet).

So, I tamed the debuff pets and checked the debuff ids in-game (apart from goats as I haven't leveled on beta yet). All but one are the same as the corresponding spell ids - Tailspin's debuff id is 90315, the spell id is 90314.

The spellname of the ability differs from the spellname of the debuff. That way tracking the spellid of the ability would result in a different spellname and thus in an insufficient UnitAura() match.

The other problem can occur if different auras are applied of the same name but different effects. This can only circumvented by testing the spellid return value of UnitAura() against the spellid used for GetSpellInfo().

There is one problem with auras of the same name though. At least if checking UnitAura with spellname+rank and not via index. If two auras of the same name are applied: which one will be returned?